My Volvo 740 has been down for two weeks now. Prior to that it had sat for a year and I could not start it due to a bad fuel pump relay which has since been bypassed. A week after buying it I began to have issues starting it. It would take a lot of pumping the gas and ignition to get a start and that gradually begin to not work to turn it on everytime and starter fluid had no effect at that point. I then inspected spark which was weak and orange. I replaced the plugs and inspected the wires and had no spark at all. Grounding the coil wire to my frame wielded no spark on the coil and the new coil. What should I inspect next on this car to resolve this? I have put on another ignition control module from the junk yard but that could had been bad.

 

So, you found it easier to "bypass" the fuel relay than to get a working one? You had weak spark, replaced the plugs and wires then you had "no spark"? Then you changed the ICM "just because"... I think you should do less, and try to diagnose your car before venturing into part swapping and modifications. Volvos are relatively easy and forgiving but still, there is no substitute for doing things right. At this point, I don't know, may be you should undo what you have done and start all over.

 

First off before you try to get Lippy with me talk what you know aboutt dog. I had to replace the bad fuel pump relay with a long wire and and off/on switch that allowed me to manually turn the pump on and off because I did not have sixty dollars for a dumb relay that would had cost me ten bux on my taurus.

The reason why I replaced the ignition module was because replacing the coil with a shiny new one made no difference to the fact I got no spark at the coil wire no matter how many different wires I tried on it and the distributer had no spark from any plugs.

The plugs and wires were traded out during testing to see if the plugs and wires that came with thecardd maybe were faulty and it made no difference.

What else you gotta say?

 

Hey look, an idiot.

 

Nah just a broke *** ****a that diddnt appreciate spending his last dime on a ****in car that broke after 2 weeks.

 

Then go back to driving the world's worst car, your Taurus. Don't buy cars with expensive parts if you aren't willing to deal with the consequences.

 

Look, Remember, I don't mean to offend you, rather point out some glaring errors in your car maintenance and repair procedures. I can tell you what I great job you did, if you want to be BSed, and your car (this unfortunate Volvo) still won't run, and you'll have learned nothing for the next time. I prefer to be honest and straightforward with people, if some can't handle it, sorry--it is at their peril. You can learn something, or not--up to you. We have all done stupid things; best realize it, ask before you do another, and mot importantly have some humility when you ask for help.

 

Tell me exactly what I did wrong instead of just saying I did something wrong and then ill tell you if that's actually what I did or not because you seem to think I did some stuff that I diddnt bro.

 

What exactly did I do that you wouldn't had done Lev after you seen that your coil had no spark?

 

you should verify that the power module is getting timing pulses when you crank the motor. no timing pulses => no spark. if you ARE getting timing pulses, then its either hte power module or the coil. no pulses, then you need to look and see if the ICU is waking up, and if the ICU is getting pulses from the hall sensor or crank position sensor (depending on what injection system it has... it could be Bosch LH2.2 (up to 1988), Bosch LH 2.4 (1989+ except 1990+ turbo), or Regina/Rex). is your car a turbo or not?

you've really given very little information that would be of use diagnosing things.

 

You mean putting a light on the dizzy's terminals to see if it lights when the rotor is on that terminal? On a ford I'd just hook my multimeter or a light to. The wires on its icm/ignitor but I don't know what wire is for what on this car's ignitor.

Alot of people ask what submodel it is I'm not sure if this 4 cylinder is the Turbo. Its a 1991 and it just says 740 on it. Not sure if it has the Regina motor I keep hearing about either.

 

if it was a turbo, there would be a turbocharger on the exhaust manifold side of the engine.

regina isn't a motor, its an alternate fuel injection and ignition system. if its a Bosch system there will be a 'mass airflow meter' (MAF, also called AMM) on the intake path between the air filter box adn the throttle body, and this will say "BOSCH" on it. if its a Bosch system, and since its a 1991, it would be LH2.4.

on a Bosch LH2.4 system, on the ignition power module, pin 5 (grey shielded wire) is the timing pulses coming from the ICU (which is mounted under the dashboard inside the car), and pin 1 (red-white wire) is the amplified timing pulses going to pin 1 of the ignition coil. a 12V test light should pulse at both of these two places when the engine is cranked. pin 4 (blue) of the power module is power, and pin 2 (black) is ground. pin 3 is the shield connection for the grey wire to pin 5.

 

Thank you so much for helping me pierce but I have a few more questions since I can atleast at this point get her to run off of Carb cleaner.

Which relays effect the fuel injectors since they are the proble m now. I've been told the fuel pump relay has two.relays in it with one for the pump and one for the injector pulse. I've been told the noise suppressor relay controls injectors and I've been told the rpm sensor does too. What else controls the injectors?

 

the fuel pump relay has two relays inside of it, one powers the ECU and comes on with the ignition, the other powers the fuel pumps and comes on when the ECU senses that the engine is turning over via the timing pulses passed on by the ICU.

the injectors on a 740/940 are powered by the 'radio surpression relay' which is under the hood on the left fender. the ECU turns this on at the same time as its powered by the ignition switch. the ground path for the injectors is via the ECU injector output, it pulses that output to ground to fire the injectors.

 

So what is the purpose of the noise relay? Did Volvo basically decide to just piggy back the Ecm relay to a random one? And do you kinda have an idea on the fail rate of this relay or the ecm for the model?

 

heh, radio relay... on the 240, the fuel injection and pump relay was over behind the glovebox, but on the 740, they consolidated all the relays in the center console, behind the ashtray, and directly below the radio. the injector current passing through this relay caused significant AM radio static, so they added a extra relay under the hood to power the injectors, and christened this relay "radio suppression relay".

fun fun fact, the late 1994 and 1995 non-turbo 940's rewired things so the under-the-hood relay ran the whole EFI show, and they moved to a separate single relay for the fuel pump, saving a few bucks.

 

Well I think I found my Volvo guy lol

That info definitely put some confusion to rest. Hopefully its that and not the ecm failing. Have you heard anything about these bad ECMs with the pink label?

 

Yes, the pink label ECU has issues with the fuel pump circuit. However, it is my understanding that the pink label ECUs were used up till around '90 so your car shouldn't have one unless someone swapped it into your car.

 

I would think that by now any bad ECUs long ago died.

 

Okay the car is running. There was some isolated blown fuse on some module way up underneath the dash near the trunk release handle. I'm not sure what its purpose is but the ten fuse had cut off my fuel relay and injectors and some how half worked when I bypassed the f.p. relay.. as for the noise suppressor some of its area did look like it had gotten hot enough to warp itself so Even though its functioning ill.replace that relay. Thank you guys.